Method and apparatus for determining metal freezing points

Abstract

A method and apparatus for determining the freezing points of a metal by inducing solidification in a cooling liquid metal sample in a supercooled state and utilizing specific detected peak values or changes in slope in a temperature/time plot as the sample cools, begins solidification and recalesces. It was found that the maximum temperature reached after the second rise, if two rises occur, the maximum of a single rise, or the temperature at which the rate of temperature drop decreases, if no temperature rise occurs, provides a useful approximation of the liquidus temperature and hence the freezing point of the sample.

What is claimed is: 
     
       1. A method of determining the freezing point of a metal sample comprising: cooling the metal sample from a liquid state to a temperature anticipated to be at or near the liquidus temperature of the metal sample;   while continuing the cooling of the metal sample, contacting the sample with a metal solid having approximately the same composition and temperature as the sample to induce solidification of the liquid sample as soon as the sample supercools;   obtaining a measure of temperature to provide a temperature/time profile as the sample solidifies; and from the temperature/time profile determining the maximum temperature reached at a second rise, if two temperature rises occur, or the maximum of a single rise, if only one rise occurs, or the temperature at which the rate of temperature drop decreases, if no temperature rise occurs, to provide an approximation of the liquidus temperature and hence the freezing point of the sample.   
     
     
       2. The method of claim 1, wherein said solid for contacting the sample comprises a wire or particle. 
     
     
       3. The method of claim 1, wherein said solid for contacting the sample comprises a previously solidified portion of the sample. 
     
     
       4. The method of claim 1, wherein said solid for contacting the sample has a solute concentration equal to or less than that of the sample.